Herpes Simplex Virus type l (HSV-l) is a ubiquitous pathogen which causes acute and latent infections in the majority of the population of the United States. The lytic cycle of HSV is the result of a coordinated temporal cascade of virus-specific protein synthesis following entry of the viral DNA into the host cell nucleus. The HSV major DNA-binding protein, commonly designated ICP8, is required for or involved in replication of the viral DNA and regulation of viral gene expression. in carrying out these functions ICP8 interacts with a variety of virus-coded and cellular macromolecules. The overall aim of this proposal is to identify and characterize functional domains within ICP8. The specific aims to accomplish this purpose are as follows: l. Mapping of the ICP8 zinc-binding domain and determination of the role of zinc in the functions of ICP8. 2. Mapping of the DNA binding-site of ICP8 and identification of specific residues involved in this interaction. 3. Identification and mapping of domains required for cooperative binding of ICP8 to nucleic acids and/or involved in conformational changes within the protein. 4. Identification and functional analysis of regions of ICP8 required for the origin-dependent synthesis of HSV DNA.